The invention relates to a holding device for electrical resistance elements to be mounted hanging in lead-through bricks in furnaces, comprising a holder provided with two opposite holding jaws for securing the terminal portions of the resistance elements, said portions being passed through corresponding holes in the lead-through brick.
Various types of such holding devices are known in the art. The mounting is usually performed by first passing the terminals of the resistance element through the holes of the lead-through brick, and thereafter setting the opposite holding jaws against the terminals, so that the latter are kept firmly in the holder, and the resistance element is given a predetermined position relative to the lead-through brick by sliding the terminal portions back into their holes until the holders rest directly on the lead-through brick. If necessary, sealing material, possible packings or the like can be inserted into the clearance between the terminal portions and the corresponding holes. The complete assembly consisting of the lead-through brick and the resistance elements is thereafter introduced into a hole of the furnace roof. Of course, before operation is begun terminal contacts must also be fitted onto the terminal portions of the resistance element so that the latter can be connected to a current source.
While this type of holding device has turned out to operate satisfactorily for several years, certain disadvantages have appeared, particularly in connection with the replacement of resistance elements. Thus, when the furnace is hot (i.e., a furnace temperature exceeding 1000.degree. C., particularly 1300.degree.-1500.degree. C.), it is very difficult to lift the assembly of resistance elements and lead-through brick, since the working conditions on the hot furnace roof are extremely severe. Under such circumstances, it has usually been necessary to pull out a damaged resistance element through the hole of the lead-through brick, causing still further damage to the U-shaped or coil-shaped heating zone of the element when the terminal portions are pulled up through the holes of the lead-through brick. Furthermore, resistance material of this kind (particularly containing substantially MoSi.sub.2) becomes very brittle during the cooling phase, which makes handling even more difficult. To lift resistance elements and lead-through bricks simultaneously has proved to be impossible under these severe temperature conditions.